As the speed and capability of computers and computer driven systems has constantly increased in modern times, so has the need for data storage devices on which information can be more compactly and densely stored. Previously, the best data storage media were magnetic, for example, magnetic tape or magnetic floppy discs.
In a magnetic data storage device, such as an audio cassette tape or a video tape, different portions of the tape are magnetized differently to represent the data being stored on the tape. When the data is to be retrieved, the tape is drawn across a magnetic head that senses the variations in the magnetization of the tape. These variations are read by the tape player and converted into the data stored on the tape. The player may then reproduce the data stored on the tape as, for example, an audiovisual program, such as a movie, or an audio program, such as a piece of music.
Magnetic storage devices have been used for storing music (e.g., cassette and eight-track tapes), television programming and movies (e.g., video tapes) and computer programs or program files (e.g., floppy discs). However, in more recent times optical discs have begun to replace magnetic data storage devices in all these area.
For example, the highest quality music is now recorded on and played from compact discs (CDs). Digital video discs (DVDs) provide a better quality video recording for movies and other audiovisual programming. CD-ROM discs provide programming for computers and, where the CD-ROM is writable, storage of computer files. Optical discs provide a digital data storage medium that allows a greater amount of data to be stored on a smaller device than was possible with magnetic data storage devices.
With an optical disc, information is stored by altering the reflectivity of successive points on the disc. To read the disc, a tightly focused laser bean is aimed at the disc. As the disc spins, the laser will pass over the different points on the disc which are arranged in a spiral. Some points will reflect the laser light back to the player; others will not reflect the light.
The disc player includes a light detector that will sense when the laser is and is not reflected. These two different possibilities, reflection—no reflection, are used to store data on the disc in a binary, digital format.
In an audio compact disc or CD, for example, data is organized into tracks. Each track consists of a sequence of reflective and non-reflective points on the disc which, when read by a CD player, can be reproduced as a song or other musical piece. The tracks on the CD are always numbered sequentially with no breaks in the numbering between one and the highest numbered track on the disc.
For example, when the CD is first inserted in a CD player, the player will typically make a quick scan of the disc to determine the total number of tracks and the total amount of time it would require to play all the music on the CD. These two pieces of information are then displayed, usually on the LCD or other display of the CD player. If the CD player is part of a computer system, a listing of the tracks may be provided on the computer monitor.
Then, as the user listens to the CD, the CD player usually displays the number of the track corresponding to the song or musical piece being played in relation to the other tracks on the disc. A great advantage of the CD format is that the CD player can quickly jump between tracks to allow the listener to hear the tracks in any order or to hear only certain tracks in a pre-programmed sequence.
However, even given this great flexibility, tracks on a CD are always sequentially numbered, e.g. 1 to 15, if there are 15 different music pieces recorded on the disc. This unbroken, sequential numbering of the tracks may, however, not be the most optimal numbering.
For example, if a particular CD is one of several in a set, it may be desirable to give each track in the set its own number. For example, it may be advantageous for the first CD in the set to have tracks 1 to 15. The second CD in the set may have tracks 16 to 30, and so on.
If this were possible, it might be easier for a listener to distinguish between the discs in the set and to reference a printed listing of the tracks on the discs so as to more readily locate a particular musical piece the listener wishes to hear. This may be particularly advantageous where several discs are in the disc player at one time such as on a turntable, or where the discs in the set are stored together in a magazine or cartridge which is fed to the CD player. With such a multi-disc player, the discs themselves are not typically viewed by the user once they are in the player or in the multi-disc cartridge. Therefore distinguishing between the discs would become easier if each disc had tracks numbered in a different range.
Additionally, an artist for artistic reasons may wish to number the tracks on a CD is some manner other than in an unbroken, numeric sequence. For example, it may be interesting to have only even or only odd numbered tracks on a CD for purely artistic reasons.
In the past, however, there has been no way to accomplish these objectives. All known optical discs and disc players organize the tracks with an unbroken, sequential numbering. Therefore, there is a need in the art for an optical disc and a method of making the same on which the tracks of the disc may be flexibly numbered in a manner other than in an unbroken, numeric sequence.